In inkjet printheads, fuse technology has been used in N-channel metal-oxide semiconductor (NMOS) chips. In these NMOS chips, fuses are selectively burned to program a bit. However, fuse technology and programming fuses in this way has drawbacks. Fuses are relatively large and fuses can be unreliable. Also, burning fuses can damage the orifice layer of the inkjet during programming and after a fuse burns out metal debris from the fuse can be drawn into the ink and cause blockage in the inkjet pen, resulting in poor quality printing.
In recent years, erasable programmable read-only memory (EPROM) devices have been developed. These EPROM devices include a conductive grid of rows and columns, without fuses. Instead, a memory cell is located at each row/column intersection. Each memory cell includes a transistor structure and two gates that are separated from each other by a thin dielectric layer. One of the gates is a floating gate and the other is a control gate or input gate. In an un-programmed memory cell, the floating gate has no charge, which causes the threshold voltage to be low. In a programmed memory cell, the floating gate is charged with electrons and the threshold voltage is higher. To program a memory cell, a programming voltage (e.g., 10 to 16 volts) is applied to the control gate and drain. This programming voltage draws excited electrons to the floating gate, thereby increasing the threshold voltage. A memory cell having a lower threshold voltage is one logic value and a memory cell having a higher threshold voltage is the other logic value.